1. Field of the Invention
This invention relates generally to a polymer composite material having improved barrier properties. More particularly, the polymer composite material of this invention is useful for forming packages or containers that have improved gas barrier properties. Containers made from this polymer composite material are ideally suited for protecting consumable products, such as foodstuffs, carbonated drinks, fruit juices, medicines and the like.
2. Related Reference
A. Usuki, M. Kato, A. Okada, T. Kurauchi, J. Appl. Polym. Sci. 63, 137(1997) describes a polypropylene composite that is made by melt mixing polypropylene with an organoclay that has been expanded with a polyolefin oligomer.
Y. Kurokawa, H. Yasuda, A. Oya, J. Mater. Sci Letters. 15, 1481 (1996) describes a polypropylene composite that is made by copolymerizing diacetone acrylamide and maleic acid modified-polypropylene in the presence of an organoclay and melt mixing with polypropylene.
T. J. Pinnavaia and Tie Lan, Chem. Mater. 6, 2216 (1994) describes oganoclays that have been expanded with epoxy resin monomers.
M. Kawasumi, N. Hasegawa, M. Kato, A. Usuki, and A. Okada, Macromolecules, 30, 6333 (1997) describes a polypropylene composite that is made by melt-mixing polypropylene, maleic anhydride modified polypropylene oligomers.
U.S. Pat. No. 4,739,007 and U.S. Pat. No. 5,164,460 disclose polyamide composite materials containing a layered clay mineral intercalated with organic onium salts.
WO 93/04118 relates to a process for forming polymeric composites which are comprised of platelet particles containing organic onium salts dispersed in a polymeric matrix.
U.S. Pat. Nos. 5,336,647 and 5,429,999 describe the preparation of layered clays containing polyalkoxylated ammonium salts. Use of these clays in polyesters, however, is not disclosed.
Among the numerous patents that describe the preparation of layered clays containing ammonium salts are U.S. Pat. Nos. 2,531,427; 2,966,506; 4,081,496; 4,105,578; 4,116,866; 4,208,218; 4,391,637; 4,410,364; 4,412,018; 4,434,075; 4,434,076; 4,450,095; 4,517,112; 4,677,158; 4,769,078; 5,110,501; and 5,334,241.
Polymers such as poly(ethylene terephthalate)(PET) are widely used in bottles and containers which are used for carbonated beverages, fruit juices, and certain foods. However, because of the limited barrier properties to oxygen, carbon dioxide and the like, PET containers, for example, are not generally used for products requiring long shelf life. It would be desirable, therefore, to provide improved gas barrier properties in polymer containers.
The present invention generally relates to a composite material comprising a polymer having dispersed therein at least one layered clay material that has been cation-exchanged with an organic cation salt. The composite material provides improved gas barrier properties in containers or bottles produced therefrom.
In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to a composition comprising (i) a layered clay material that has been cation-exchanged with an organic cation salt represented by the formula (I): 
wherein M is nitrogen or phosphorous, Xxe2x88x92 is a halide, hydroxide, or acetate anion, R1 is a straight or branched alkyl group having at least 8 carbon atoms, and R2, R3, and R4 are independently hydrogen or a straight or branched alkyl group having 1 to 22 carbon atoms; and (ii) at least one expanding agent, wherein the cation-exchanged clay material contains platelet particles and the expanding agent separates the platelet particles.
In another aspect, the present invention relates to a composite comprising a polymer having dispersed therein (i) at least one layered clay material that has been cation-exchanged with an organic cation salt having at least one straight or branched alkyl group having at least 8 carbon atoms; and (ii) at least one expanding agent that is compatible with the polymer, wherein the cation-exchanged clay material contains platelet particles and the expanding agent separates the platelet particles, and wherein the platelet particles are dispersed in the polymer such that the basal spacing between the platelet particles is greater than about 3 nm.
In yet another aspect, the present invention relates to a composite comprising a 
polymer having dispersed therein (i) a layered clay material that has been cation-exchanged with an organic cation salt represented by Formula (I):
wherein M is nitrogen or phosphorous, Xxe2x88x92 is a halide, hydroxide, or acetate anion, R1 is a straight or branched alkyl group having at least 8 carbon atoms, and R2, R3, and R4 are independently hydrogen or a straight or branched alkyl group having 1 to 22 carbon atoms; and (ii) at least one expanding agent that is compatible with the polymer, wherein the cation-exchanged clay material contains platelet particles and the expanding agent separates the platelet particles.
Additional advantages of the invention will be set forth in part in the detailed description, including the figures, which follow, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory of preferred embodiments of the invention, and are not restrictive of the invention, as claimed.